A simple way to measure whether the circuit is leaking with a multimeter
Use a multimeter to measure whether the 220V line is leaking. The easiest way is to cut off the power first, put the multimeter to the electric barrier (500 ohms), connect the neutral wire and live wire to the ground wire with two pens of the multimeter, if the measured result is 0 , so that you can determine which wire is grounded, and there will be leakage.
To measure whether the 220V line is leaking or not, it should be accurate to use a 500V or 1000V shaking meter to measure whether it is accurate. It is not appropriate to use a multimeter to measure whether the 220V line is leaking. Test with a double-pole leakage circuit breaker in normal use. Connect the leakage circuit breaker and close the leakage circuit breaker to open immediately, and its reset button protrudes again (Note: If the reset button does not protrude, it is overload protection and short circuit. Protection trip) proves that there is leakage in the line. This method is relatively simple and accurate.
The problem of measuring 220V leakage with a multimeter is not suitable, because what you want to measure is the leakage current. The multimeter is weak in measuring weak AC current, and it is troublesome to measure inaccurately. If you insist on measuring, you need to use a current transformer. Use a clamp meter to measure, but choose a clamp meter with a suitable range and better sensitivity.
If you suspect that the circuit is leaking, you can use a circuit breaker with a leak protection to judge, judge the range of the leakage segment by segment, and troubleshoot.
As for using electricity to block the leakage of the measurement line, I don't think it is appropriate. Because since it is a leakage, the resistance between the live wire and the protective ground is not infinite, but the voltage of the multimeter is not enough to explain the insulation between them, that is to say, the insulation resistance at 9V is completely different from that at 220V. Therefore, the insulation resistance is measured at a condition higher than the electrical voltage to obtain reliable data. So you have to use a shaker.
Of course, if you just test whether there is a short circuit or a path between the live wire and the protective ground, it is also possible to use a multimeter to block it. Just can't measure the insulation data between them.
If the insulation of the line is damaged, it can be seen visually, and it can be dealt with at that time. Another situation is that the roll skin is not damaged, but it is a little cracked, resulting in some grounding in wet conditions, or the damaged place is very hidden, and people cannot directly see it with the naked eye. At this time, you can cut off the power of the line and shake it directly with the shaker. For low voltage circuits, a 500 volt megger should be used. Measured against ground, if the insulation is less than 0.5 megohms. It can be considered that the insulation is not very good and should be checked section by section. One thing to note is that when measuring with a megger, no electrical appliances can be connected to the circuit. Otherwise, the measured value may be inaccurate.
If you use a multimeter to check for leakage. Maybe not quite right. Because the voltage of the general meter is very low. Only when the leakage is serious can it be detected.
Let me say something other than the subject, it is best to use a leakage protector switch for the socket at home. In this way, once a leakage occurs, the power supply can be cut off quickly to ensure personal safety.
1. Power-off measurement: turn off and disconnect all electrical appliances, use a multimeter with RX10K gear, one test lead is connected to the live wire, and the other test lead is grounded (or faucet). It should show infinite resistance, otherwise there will be leakage.
2. Live measurement: Use a multimeter with a 250-volt AC voltage range to measure the metal shell of the electrical appliance that is suspected of leakage. One test lead is connected to the shell, and the other test lead is grounded (or the faucet). When the pointer shows a voltage higher than 30-50 volts, replace it Use AC 50 volts. If the power supply is confirmed to be higher than 30 volts, it is a leakage, and lower than 30 volts is normal. Then swap the zero and fire power supply plug wires and measure again to confirm.
3. Leakage measurement between live wire and neutral wire (or live wire and live wire): turn off and disconnect all electrical appliances, measure the resistance between live wire and neutral wire, it should be infinite, otherwise it is leakage.
The accuracy rate of the above method for troubleshooting is 99.9%, convenient, fast and practical, and the megohm special shaker is only used in engineering, and the use efficiency is low in maintenance. Only when the multimeter is confirmed to be good, but the line is indeed leaking, can it be used Shake the meter, but the leakage cannot be detected by the multimeter.
